Conventionally, as shown in FIGS. 7, 8, and 9, a train, for example, a train 101 composed of twelve railway cars is configured such that a plurality of cars A1′ to A12′ are coupled to one another by means of couplers B1 to B11 each provided between the cars. And, energy absorbing elements that are tubular with rectangular cross-section are supported by a vehicle body frame, thereby forming energy absorbing structures. For example, as shown in FIGS. 8 and 9, in a front car and a subsequent car, energy absorbing elements 11′ and 12′ are placed in front of and behind buffing gears 13 and 14 coupled to couplers B1, respectively.
The applicant disclosed the above-described structure, in which bellows-like deformation stably takes place and the relationship between a width and a plate thickness of an impact absorbing member, i.e., an energy absorbing element satisfies a predetermined formula to reduce crash load and acceleration caused by crash between vehicle body frames (see Japanese Laid-Open Patent Application Publication No. 2001-334316). However, such a structure does not take best use of a collective structure of these energy absorbing structures of the entire train into consideration.
Conventionally, various types of energy absorbing structures between cars of the train have been proposed.
(1) The energy absorbing structure disclosed in Japanese Laid-Open Patent Application Publication No. Hei. 7-267086 is configured such that an annular member having a cylindrical outer surface is provided on one of a plurality of cars coupled to one another, and a support member having an inner cylindrical portion opposed to the cylindrical outer face is provided on an opposite car. The annular member and the support member are coupled by means of an annular coupling element, and an energy absorbing means is provided between them.
(2) The energy absorbing structure disclosed in Japanese Laid-Open Patent Application Publication No. 2000-313334 is configured to appropriately release a crash impact force that exceeds an upper limit of a mechanical strength of a coupler or a buffing gear to thereby reduce damage to the cars. For this purpose, a release mechanism for releasing a load acting on the buffing gear when the crash impact force that exceeds the upper limit of mechanical strength of the coupler or the buffing gear is generated, comprises a link mechanism having a variable spacing between the coupler and the buffing gear, and a restricting member capable of restricting an operation of the link mechanism when the impact force below the upper limit acts on the link mechanism and of releasing restriction of the operation when the impact force that exceeds the upper limit acts on the link mechanism.
(3) The energy absorbing structure disclosed in Japanese Laid-Open Patent Application Publication No. 2001-260881 comprises a buffing gear provided within a holder storage portion and an energy absorbing element provided between a rear end of the holder end and a rear stopper. Upon the crash impact force that exceeds the upper limit of mechanical strength of the coupler or the buffing gear acting on the car, in this energy absorbing structure, the holder slides to allow a crash energy to be absorbed by deformation of the energy absorbing element in order to reduce the damage to the car body.
(4) NEC TRAIN SETS—PRACTICAL CONSIDERATIONS FOR THE INTRODUCTION OF A CRASH ENERGY MANAGEMENT SYSTEM (Rail Vehicle Crashworthiness Symposium Jun. 24-26 1996) proposes a crash energy management system (see FIGS. 1 and 2 in the same literature document). In the crash energy management system, an energy absorption capacity at 1st interface between a front car and a subsequent car is set larger than an energy absorption capacity at 2nd interface between cars on the inner side of the train. The reason why the energy absorption capacity at the interface between the cars at an end portion of the train is set larger than the energy absorption capacity at the interface between the inner-side cars of the train is that the interface at the end portion of the train has subsequent cars more than the interface between the inner cars, and therefore needs to support more mass.
However, the prior arts disclosed in the above described Publications have the following problems.
(1) In the prior arts disclosed in Japanese Laid-Open Patent Application Publication Nos. 7-267086, 2000-313334, and 2001-260881, the energy absorbing structure between cars is provided at plural positions of the train, but a collective structure of these energy absorbing structures does not efficiently function.
(2) In the prior art disclosed in the literature document (crash energy management system), if a compressive load in energy absorption of the energy absorbing structure at the 1st interface is set smaller than that at the 2nd interface, then compressive deformation greatly occurs only at the 1st interface and the energy is not absorbed efficiently at the 2nd interface. As a result, the energy absorption capacity in the entire train is not sufficiently increased.
Since subsequent cars are fewer at the center portion of the train than at the front portion of the train, it is advantageous that the compressive load in energy absorption at the center portion is reduced, because this reduce impact acceleration in crash.